University of Pennsylvania, Philadelphia, April 1, 1878. Sir : I have the honor to transmit herewith my final report upon the botanical collections made by the parties under your charge. In doing so, it is but fair to state how little of whatever merit the report may have is due to myself, and how much to those who have assisted in collecting the material, and to those who subsequently aided in naming and describing it. Dr. George Engelmann, of Saint Louis, has furnished reports upon the numerous orders and genera that he is our acknowledged authority upon, and these alone form no inconsiderable part of the whole. Professor Gray, of Cambridge, has throughout kindly settled all doubtful points of nomenclature referred to him. Without his advice and assistance, it would have been impossible for me to have completed the work. The same may be said of the services of Mr. Sereno Watson. He has also furnished the list and descriptions of the Leguminosse. Prof Thomas C. Porter, of Easton, has worked up the Scrophulariaceae, Polemoniacese, Labiates, Borraginacese, and Polygonacese, orders which together comprise a large part of the descriptive text. Mr. M. S. Bebb, of Fountain dale, III, has written the account of the Willows, which are confessedly among the most difficult of all Americangenera. Dr. George Vasey, Botanist to the Department of Agriculture atWashington, D. C, has made a careful report on the Grasses collected bythe Expedition; and Mr. William Boott, of Boston, Mass., contributes thepaper on Carex. x^^l n HOT